diff --git a/assets/Localizable.xcstrings b/assets/Localizable.xcstrings
index aed5d7a..1eeb33f 100644
--- a/assets/Localizable.xcstrings
+++ b/assets/Localizable.xcstrings
@@ -129,6 +129,22 @@
         }
       }
     },
+    "All Apps Are Up to Date": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "All Apps Are Up to Date"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "全部应用已是最新"
+          }
+        }
+      }
+    },
     "App Repository": {
       "localizations": {
         "en": {
@@ -369,6 +385,22 @@
         }
       }
     },
+    "Change Installed Version?": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Change Installed Version?"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "更改已安装版本？"
+          }
+        }
+      }
+    },
     "Check Again": {
       "localizations": {
         "en": {
@@ -689,6 +721,22 @@
         }
       }
     },
+    "Downgrade": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Downgrade"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "降级"
+          }
+        }
+      }
+    },
     "Download Size": {
       "localizations": {
         "en": {
@@ -753,6 +801,38 @@
         }
       }
     },
+    "Install %@ on %@? The installed version could not be compared.": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Install %1$@ on %2$@? The installed version could not be compared."
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "在 %2$@ 上安装 %1$@？无法比较已安装版本。"
+          }
+        }
+      }
+    },
+    "Install %@ on %@? This is an older version and may not work with existing app data.": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Install %1$@ on %2$@? This is an older version and may not work with existing app data."
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "在 %2$@ 上安装 %1$@？这是较旧的版本，可能无法使用现有应用数据。"
+          }
+        }
+      }
+    },
     "Install Xcode to add iPhone and iPad simulators.": {
       "localizations": {
         "en": {
@@ -913,6 +993,38 @@
         }
       }
     },
+    "Newer compatible versions of your installed apps will appear here.": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Newer compatible versions of your installed apps will appear here."
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "已安装应用有兼容的新版本时，会显示在这里。"
+          }
+        }
+      }
+    },
+    "Newer versions for your simulator.": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Newer versions for your simulator."
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "适用于此模拟器的新版本。"
+          }
+        }
+      }
+    },
     "No Apps Available": {
       "localizations": {
         "en": {
@@ -1889,6 +2001,22 @@
         }
       }
     },
+    "Update": {
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Update"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "更新"
+          }
+        }
+      }
+    },
     "Update SimStore to read this app catalog.": {
       "localizations": {
         "en": {
diff --git a/src/AppCatalog.swift b/src/AppCatalog.swift
index 8fb0f33..12fe392 100644
--- a/src/AppCatalog.swift
+++ b/src/AppCatalog.swift
@@ -34,7 +34,18 @@ struct CatalogApp: Identifiable, Hashable, Sendable {
   }
 
   func recommendedVersion(for runtime: String) -> CatalogVersion {
-    versions.first { $0.isCompatible(with: runtime) } ?? latestVersion
+    latestCompatibleVersion(for: runtime) ?? latestVersion
+  }
+
+  func latestCompatibleVersion(for runtime: String) -> CatalogVersion? {
+    versions.first { $0.isCompatible(with: runtime) }
+  }
+
+  func availableUpdate(from installedVersion: String?, runtime: String) -> CatalogVersion? {
+    guard let version = latestCompatibleVersion(for: runtime),
+      version.comparison(with: installedVersion) == .orderedDescending
+    else { return nil }
+    return version
   }
 }
 
@@ -55,6 +66,14 @@ struct CatalogVersion: Identifiable, Hashable, Sendable {
     else { return false }
     return installed >= minimum
   }
+
+  func comparison(with installedVersion: String?) -> ComparisonResult? {
+    guard let installedVersion, let installed = CatalogVersionNumber(installedVersion),
+      let candidate = CatalogVersionNumber(version)
+    else { return nil }
+    if candidate == installed { return .orderedSame }
+    return candidate > installed ? .orderedDescending : .orderedAscending
+  }
 }
 
 enum AppCatalogError: LocalizedError, Equatable {
diff --git a/src/AppInstallButton.swift b/src/AppInstallButton.swift
index d685fda..93ac877 100644
--- a/src/AppInstallButton.swift
+++ b/src/AppInstallButton.swift
@@ -5,52 +5,80 @@ struct AppInstallButton: View {
   let version: CatalogVersion
   let device: SimulatorDevice
   let store: AppInstallationStore
-  let isInstalled: Bool?
+  let installedApps: InstalledAppsStore
   var allowsIncompatible = false
+  var allowsVersionChanges = false
   var isDefaultAction = false
 
-  private enum Action: CaseIterable {
-    case install, open, cancel, installing, canceling, opening, uninstalling
+  @State private var showsConfirmation = false
+  @State private var pendingVersionChange: VersionChange?
 
-    var title: String {
-      switch self {
-      case .install: String(localized: "Install")
-      case .open: String(localized: "Open")
-      case .cancel: String(localized: "Cancel")
-      case .installing: AppInstallationPhase.installing.title
-      case .canceling: AppInstallationPhase.canceling.title
-      case .opening: AppInstallationPhase.opening.title
-      case .uninstalling: AppInstallationPhase.uninstalling.title
-      }
-    }
+  private struct VersionChange {
+    let app: CatalogApp
+    let version: CatalogVersion
+    let device: SimulatorDevice
+    let action: AppInstallationAction
+  }
+
+  private var isInstalled: Bool? {
+    installedApps.isInstalled(bundleID: app.bundleID, deviceID: device.id)
+  }
+
+  private var idleAction: AppInstallationAction {
+    .forVersion(
+      version, installed: installedApps.application(bundleID: app.bundleID, deviceID: device.id),
+      allowsChanges: allowsVersionChanges)
   }
 
   private var phase: AppInstallationPhase? {
     store.phase(appID: app.id, deviceID: device.id)
   }
 
-  private var action: Action {
+  private var action: AppInstallationAction {
     switch phase {
     case .downloading, .verifying, .extracting: .cancel
     case .installing: .installing
     case .canceling: .canceling
     case .opening: .opening
     case .uninstalling: .uninstalling
-    case nil: isInstalled == true ? .open : .install
+    case nil: idleAction
     }
   }
 
   private var enabled: Bool {
     if let phase { return phase.canCancel }
     guard device.state == "Booted", let isInstalled else { return false }
-    return isInstalled || allowsIncompatible || version.isCompatible(with: device.runtime)
+    if idleAction == .open { return isInstalled }
+    return allowsIncompatible || version.isCompatible(with: device.runtime)
   }
 
   var body: some View {
-    if phase == nil {
-      button.buttonStyle(.borderedProminent)
-    } else {
-      button.buttonStyle(.bordered)
+    Group {
+      if phase == nil {
+        button.buttonStyle(.borderedProminent)
+      } else {
+        button.buttonStyle(.bordered)
+      }
+    }
+    .alert(
+      "Change Installed Version?", isPresented: $showsConfirmation, presenting: pendingVersionChange
+    ) { request in
+      Button("Cancel", role: .cancel) {}
+      Button(role: .destructive) {
+        store.replace(app: request.app, version: request.version, on: request.device)
+      } label: {
+        Text(verbatim: request.action.title)
+      }
+    } message: { request in
+      if request.action == .downgrade {
+        Text(
+          "Install \(request.version.version) on \(request.device.name)? This is an older version and may not work with existing app data."
+        )
+      } else {
+        Text(
+          "Install \(request.version.version) on \(request.device.name)? The installed version could not be compared."
+        )
+      }
     }
   }
 
@@ -58,12 +86,20 @@ struct AppInstallButton: View {
     Button {
       switch action {
       case .install: store.install(app: app, version: version, on: device)
+      case .update, .downgrade, .replace:
+        if action.needsConfirmation {
+          pendingVersionChange = VersionChange(
+            app: app, version: version, device: device, action: action)
+          showsConfirmation = true
+        } else {
+          store.replace(app: app, version: version, on: device)
+        }
       case .open: store.open(app: app, on: device)
       case .cancel: store.cancel(appID: app.id, deviceID: device.id)
       case .installing, .canceling, .opening, .uninstalling: break
       }
     } label: {
-      StableSizeView(action, states: Action.allCases) { value in
+      StableSizeView(action, states: AppInstallationAction.allCases) { value in
         Text(verbatim: value.title)
       }
       .lineLimit(1)
diff --git a/src/AppInstallationAction.swift b/src/AppInstallationAction.swift
new file mode 100644
index 0000000..bb4df1f
--- /dev/null
+++ b/src/AppInstallationAction.swift
@@ -0,0 +1,40 @@
+import Foundation
+
+enum AppInstallationAction: CaseIterable {
+  case install, open, update, downgrade, replace
+  case cancel, installing, canceling, opening, uninstalling
+
+  var title: String {
+    switch self {
+    case .install: String(localized: "Install")
+    case .open: String(localized: "Open")
+    case .update: String(localized: "Update")
+    case .downgrade: String(localized: "Downgrade")
+    case .replace: Self.install.title
+    case .cancel: String(localized: "Cancel")
+    case .installing: AppInstallationPhase.installing.title
+    case .canceling: AppInstallationPhase.canceling.title
+    case .opening: AppInstallationPhase.opening.title
+    case .uninstalling: AppInstallationPhase.uninstalling.title
+    }
+  }
+
+  var isVersionChange: Bool {
+    self == .update || self == .downgrade || self == .replace
+  }
+
+  var needsConfirmation: Bool { self == .downgrade || self == .replace }
+
+  static func forVersion(
+    _ version: CatalogVersion, installed: SimulatorApplication?, allowsChanges: Bool
+  ) -> Self {
+    guard let installed else { return .install }
+    guard allowsChanges, installed.isUserApplication else { return .open }
+    switch version.comparison(with: installed.version) {
+    case .orderedSame: return .open
+    case .orderedDescending: return .update
+    case .orderedAscending: return .downgrade
+    case nil: return .replace
+    }
+  }
+}
diff --git a/src/AppInstallationStore.swift b/src/AppInstallationStore.swift
index 1d7d00b..b0d8c65 100644
--- a/src/AppInstallationStore.swift
+++ b/src/AppInstallationStore.swift
@@ -15,6 +15,7 @@ final class AppInstallationStore {
   private(set) var uninstalledApp: Key?
   @ObservationIgnored private let installer: AppInstaller
   @ObservationIgnored private let didInstall: @MainActor (SimulatorApplication, String) -> Void
+  @ObservationIgnored private let didReplace: @MainActor (SimulatorApplication, String) -> Void
   @ObservationIgnored private let didUninstall: @MainActor (String, String) -> Void
   @ObservationIgnored private let showDevice: @MainActor (SimulatorDevice) async throws -> Void
   @ObservationIgnored private let didOpen: @MainActor (String, String) -> Void
@@ -25,11 +26,13 @@ final class AppInstallationStore {
     installer: AppInstaller = AppInstaller(),
     showDevice: @escaping @MainActor (SimulatorDevice) async throws -> Void,
     didInstall: @escaping @MainActor (SimulatorApplication, String) -> Void = { _, _ in },
+    didReplace: @escaping @MainActor (SimulatorApplication, String) -> Void = { _, _ in },
     didUninstall: @escaping @MainActor (String, String) -> Void = { _, _ in },
     didOpen: @escaping @MainActor (String, String) -> Void = { _, _ in }
   ) {
     self.installer = installer
     self.didInstall = didInstall
+    self.didReplace = didReplace
     self.didUninstall = didUninstall
     self.showDevice = showDevice
     self.didOpen = didOpen
@@ -44,6 +47,17 @@ final class AppInstallationStore {
   }
 
   func install(app: CatalogApp, version: CatalogVersion, on device: SimulatorDevice) {
+    startInstallation(app: app, version: version, on: device, completion: didInstall)
+  }
+
+  func replace(app: CatalogApp, version: CatalogVersion, on device: SimulatorDevice) {
+    startInstallation(app: app, version: version, on: device, completion: didReplace)
+  }
+
+  private func startInstallation(
+    app: CatalogApp, version: CatalogVersion, on device: SimulatorDevice,
+    completion: @escaping @MainActor (SimulatorApplication, String) -> Void
+  ) {
     let key = Key(appID: app.id, deviceID: device.id)
     guard jobs[key] == nil else { return }
     let request = UUID()
@@ -63,7 +77,7 @@ final class AppInstallationStore {
             phases[key] = phase
           }
         }
-        didInstall(
+        completion(
           SimulatorApplication(
             bundleID: app.bundleID, version: version.version, isUserApplication: true),
           device.id)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d5322ae..d3f37cc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -19,6 +19,7 @@ add_executable(SimStore MACOSX_BUNDLE
     AppPackage.swift
     AppInstaller.swift
     AppInstallationStore.swift
+    AppInstallationAction.swift
     AppInstallButton.swift
     AppUninstallButton.swift
     DownloadProgressView.swift
diff --git a/src/CatalogAppCard.swift b/src/CatalogAppCard.swift
index b1831d3..dca0cca 100644
--- a/src/CatalogAppCard.swift
+++ b/src/CatalogAppCard.swift
@@ -5,11 +5,12 @@ struct CatalogAppCard: View {
   let device: SimulatorDevice
   let installedApps: InstalledAppsStore
   let installations: AppInstallationStore
-  let showsInstallation: Bool
+  let section: LibrarySection
   @FocusState.Binding var focusedAppID: String?
   let showDetails: () -> Void
 
   private var runtime: String { device.runtime }
+  private var showsInstallation: Bool { section != .discover }
 
   var body: some View {
     let version = app.recommendedVersion(for: runtime)
@@ -35,35 +36,16 @@ struct CatalogAppCard: View {
       .allowsHitTesting(false)
       .accessibilityHidden(true)
       HStack {
-        HStack(spacing: 4) {
-          if let phase = installations.phase(appID: app.id, deviceID: device.id), !showsInstallation
-          {
-            Text(verbatim: phase.summary(totalBytes: version.size)).foregroundStyle(.secondary)
-              .monospacedDigit()
-          } else if installations.error(appID: app.id, deviceID: device.id) != nil {
-            Image(systemName: "exclamationmark.triangle").foregroundStyle(.red)
-            versionLabel(version)
-          } else if showsInstallation {
-            versionLabel(version)
-          } else if !version.isCompatible(with: runtime) {
-            Label("iOS \(version.minSimulatorOS)+", systemImage: "exclamationmark.triangle")
-              .foregroundStyle(.orange)
-          } else {
-            Text(verbatim: version.version).monospacedDigit()
-          }
-        }
-        .lineLimit(1)
-        .allowsHitTesting(false)
-        .accessibilityHidden(true)
+        versionSummary(version)
         Spacer(minLength: 4)
-        if !showsInstallation {
+        if section != .installed {
           Text(verbatim: ByteCountFormatter.string(fromByteCount: version.size, countStyle: .file))
             .foregroundStyle(.secondary)
             .lineLimit(1)
             .allowsHitTesting(false)
             .accessibilityHidden(true)
         }
-        if showsInstallation {
+        if section == .installed {
           AppUninstallButton(
             app: app, device: device, installedApps: installedApps, installations: installations
           )
@@ -73,7 +55,7 @@ struct CatalogAppCard: View {
         }
         AppInstallButton(
           app: app, version: version, device: device, store: installations,
-          isInstalled: installedApps.isInstalled(bundleID: app.bundleID, deviceID: device.id)
+          installedApps: installedApps, allowsVersionChanges: section == .updates
         )
         .controlSize(.small)
         .accessibilityIdentifier("catalog-install-\(app.id)")
@@ -93,9 +75,9 @@ struct CatalogAppCard: View {
       .accessibilityValue(
         Text(
           verbatim:
-            showsInstallation
-            ? "\(app.displayDescription) · \(installedVersion)"
-            : "\(app.displayDescription) · \(version.version) · \(version.minimumOSLabel) · \(ByteCountFormatter.string(fromByteCount: version.size, countStyle: .file))"
+            section == .installed
+            ? "\(app.displayDescription) · \(versionText(version))"
+            : "\(app.displayDescription) · \(versionText(version)) · \(version.minimumOSLabel) · \(ByteCountFormatter.string(fromByteCount: version.size, countStyle: .file))"
         )
       )
       .accessibilityHint(Text("View app details and versions"))
@@ -117,7 +99,37 @@ struct CatalogAppCard: View {
       ?? String(localized: "Version Unavailable")
   }
 
-  private func versionLabel(_ version: CatalogVersion) -> some View {
-    Text(verbatim: showsInstallation ? installedVersion : version.version).monospacedDigit()
+  private func versionText(_ version: CatalogVersion) -> String {
+    if !showsInstallation { return version.version }
+    if section == .updates,
+      version.comparison(
+        with: installedApps.application(bundleID: app.bundleID, deviceID: device.id)?.version)
+        == .orderedDescending
+    {
+      return "\(installedVersion) → \(version.version)"
+    }
+    return installedVersion
+  }
+
+  private func versionSummary(_ version: CatalogVersion) -> some View {
+    HStack(spacing: 4) {
+      if let phase = installations.phase(appID: app.id, deviceID: device.id),
+        section != .installed, phase != .uninstalling
+      {
+        Text(verbatim: phase.summary(totalBytes: version.size)).foregroundStyle(.secondary)
+          .monospacedDigit()
+      } else if installations.error(appID: app.id, deviceID: device.id) != nil {
+        Image(systemName: "exclamationmark.triangle").foregroundStyle(.red)
+        Text(verbatim: versionText(version)).monospacedDigit()
+      } else if showsInstallation || version.isCompatible(with: runtime) {
+        Text(verbatim: versionText(version)).monospacedDigit()
+      } else {
+        Label("iOS \(version.minSimulatorOS)+", systemImage: "exclamationmark.triangle")
+          .foregroundStyle(.orange)
+      }
+    }
+    .lineLimit(1)
+    .allowsHitTesting(false)
+    .accessibilityHidden(true)
   }
 }
diff --git a/src/CatalogAppDetailView.swift b/src/CatalogAppDetailView.swift
index 9353afa..29c15f0 100644
--- a/src/CatalogAppDetailView.swift
+++ b/src/CatalogAppDetailView.swift
@@ -183,10 +183,27 @@ struct CatalogAppDetailView: View {
           .accessibilityIdentifier("detail-uninstall")
         }
         Spacer()
+        if AppInstallationAction.forVersion(
+          version,
+          installed: installedApps.application(bundleID: app.bundleID, deviceID: device.id),
+          allowsChanges: true
+        ).isVersionChange {
+          Button {
+            installations.open(app: app, on: device)
+          } label: {
+            Text(verbatim: AppInstallationAction.open.title)
+          }
+          .buttonStyle(.bordered)
+          .disabled(
+            device.state != "Booted"
+              || installations.phase(appID: app.id, deviceID: device.id) != nil
+          )
+          .accessibilityIdentifier("detail-open")
+        }
         AppInstallButton(
           app: app, version: version, device: device, store: installations,
-          isInstalled: installedApps.isInstalled(bundleID: app.bundleID, deviceID: device.id),
-          allowsIncompatible: true, isDefaultAction: true
+          installedApps: installedApps,
+          allowsIncompatible: true, allowsVersionChanges: true, isDefaultAction: true
         )
         .accessibilityIdentifier("detail-install")
       }
diff --git a/src/CatalogBrowserView.swift b/src/CatalogBrowserView.swift
index b1f1864..9564e77 100644
--- a/src/CatalogBrowserView.swift
+++ b/src/CatalogBrowserView.swift
@@ -18,8 +18,8 @@ struct CatalogBrowserView: View {
   @State private var showsSimulator = false
   @FocusState private var focusedAppID: String?
 
-  private var categories: [String] {
-    Array(Set(availableApps?.flatMap(\.categories) ?? [])).sorted()
+  private var categories: [String]? {
+    availableApps.map { Array(Set($0.flatMap(\.categories))).sorted() }
   }
 
   private var availableApps: [CatalogApp]? {
@@ -27,6 +27,7 @@ struct CatalogBrowserView: View {
     switch section {
     case .discover: return installedApps.discoverableApps(in: catalog, for: device.id)
     case .installed: return installedApps.installedApps(in: catalog, for: device.id)
+    case .updates: return installedApps.updatableApps(in: catalog, for: device)
     }
   }
 
@@ -92,7 +93,7 @@ struct CatalogBrowserView: View {
       dismissDetails(matching: uninstalled)
     }
     .onChange(of: categories) { _, values in
-      guard availableApps != nil else { return }
+      guard let values else { return }
       if !category.isEmpty && !values.contains(category) { category = "" }
     }
     .sheet(item: $selectedApp) { app in
@@ -158,7 +159,7 @@ struct CatalogBrowserView: View {
       HStack(spacing: 12) {
         Picker("Category", selection: $category) {
           Text("All Apps").tag("")
-          ForEach(categories, id: \.self) { value in
+          ForEach(categories ?? [], id: \.self) { value in
             Text(verbatim: CatalogCategory.title(value)).tag(value)
           }
         }
@@ -184,9 +185,24 @@ struct CatalogBrowserView: View {
           Text("Apps you install from this catalog will appear here.")
         }
         .frame(maxWidth: .infinity, maxHeight: .infinity)
+      } else if availableApps.isEmpty && section == .updates {
+        ContentUnavailableView {
+          Label {
+            Text("All Apps Are Up to Date")
+          } icon: {
+            Image(systemName: "checkmark.circle").foregroundStyle(.green)
+          }
+        } description: {
+          Text("Newer compatible versions of your installed apps will appear here.")
+        }
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
       } else if availableApps.isEmpty {
         ContentUnavailableView {
-          Label("All Apps Are Installed", systemImage: "checkmark.circle")
+          Label {
+            Text("All Apps Are Installed")
+          } icon: {
+            Image(systemName: "checkmark.circle").foregroundStyle(.green)
+          }
         } description: {
           Text("Every app in the catalog is already installed on this simulator.")
         }
@@ -216,7 +232,7 @@ struct CatalogBrowserView: View {
                     let app = visibleApps[index]
                     CatalogAppCard(
                       app: app, device: device, installedApps: installedApps,
-                      installations: installations, showsInstallation: section == .installed,
+                      installations: installations, section: section,
                       focusedAppID: $focusedAppID,
                       showDetails: { selectedApp = app }
                     )
diff --git a/src/ContentView.swift b/src/ContentView.swift
index 70dd860..4418d3b 100644
--- a/src/ContentView.swift
+++ b/src/ContentView.swift
@@ -53,6 +53,9 @@ struct ContentView: View {
         didInstall: { application, deviceID in
           installedApps.recordInstallation(application, deviceID: deviceID)
         },
+        didReplace: { application, deviceID in
+          installedApps.recordReplacement(application, deviceID: deviceID)
+        },
         didUninstall: { bundleID, deviceID in
           installedApps.recordUninstallation(bundleID: bundleID, deviceID: deviceID)
         },
@@ -74,12 +77,17 @@ struct ContentView: View {
     discovery?.deviceManager
   }
 
+  private var updateCount: Int? {
+    guard let device = simulators.selectedDevice, let catalog = catalog.catalog else { return nil }
+    return installedApps.updatableApps(in: catalog, for: device, includingRecent: false)?.count
+  }
+
   var body: some View {
     NavigationSplitView {
       GeometryReader { geometry in
         SidebarView(
           discovery: discovery, isChecking: simulators.isChecking, needsXcode: needsXcode,
-          section: $librarySection,
+          section: $librarySection, updateCount: updateCount,
           selectedDeviceID: simulators.selectedDeviceID,
           startingDeviceIDs: simulators.startingDeviceIDs, selectDevice: simulators.selectDevice,
           openRepository: openRepository
@@ -123,6 +131,7 @@ struct ContentView: View {
     .navigationSplitViewStyle(.balanced)
     .frame(minWidth: 900, minHeight: 600)
     .task { await simulators.refresh() }
+    .onChange(of: librarySection) { _, _ in installedApps.clearRecentInstallations() }
     .task(id: shouldMonitorState) {
       while shouldMonitorState && !Task.isCancelled {
         do {
diff --git a/src/InstalledAppsStore.swift b/src/InstalledAppsStore.swift
index 93eb408..b2b9944 100644
--- a/src/InstalledAppsStore.swift
+++ b/src/InstalledAppsStore.swift
@@ -10,6 +10,7 @@ final class InstalledAppsStore {
   private(set) var isLoading = false
   private(set) var error: String?
   private var recentInstallations: Set<String> = []
+  private var recentReplacements: Set<String> = []
 
   @ObservationIgnored
   private let load: @Sendable (SimulatorDevice) async throws -> [SimulatorApplication]
@@ -36,6 +37,25 @@ final class InstalledAppsStore {
     return catalog.apps.filter { installed.contains($0.bundleID.lowercased()) }
   }
 
+  func updatableApps(
+    in catalog: AppCatalog, for device: SimulatorDevice, includingRecent: Bool = true
+  ) -> [CatalogApp]? {
+    guard device.state == "Booted", self.deviceID == device.id, applications != nil else {
+      return nil
+    }
+    return catalog.apps.filter { app in
+      guard let installed = application(bundleID: app.bundleID, deviceID: device.id),
+        installed.isUserApplication
+      else { return false }
+      if app.availableUpdate(from: installed.version, runtime: device.runtime) != nil {
+        return true
+      }
+      return includingRecent && recentReplacements.contains(app.bundleID.lowercased())
+        && app.latestCompatibleVersion(for: device.runtime)?.comparison(with: installed.version)
+          == .orderedSame
+    }
+  }
+
   func application(bundleID: String, deviceID: String) -> SimulatorApplication? {
     guard self.deviceID == deviceID else { return nil }
     return applications?.first { $0.bundleID.caseInsensitiveCompare(bundleID) == .orderedSame }
@@ -50,20 +70,34 @@ final class InstalledAppsStore {
     }
   }
 
-  func clearRecentInstallations() { recentInstallations = [] }
+  func clearRecentInstallations() {
+    recentInstallations = []
+    recentReplacements = []
+  }
 
   func removeRecentInstallation(bundleID: String, deviceID: String) {
     guard self.deviceID == deviceID else { return }
     recentInstallations.remove(bundleID.lowercased())
+    recentReplacements.remove(bundleID.lowercased())
   }
 
   func recordInstallation(_ application: SimulatorApplication, deviceID: String) {
     guard self.deviceID == deviceID else { return }
+    mergeInstallation(application)
+    recentInstallations.insert(application.bundleID.lowercased())
+  }
+
+  func recordReplacement(_ application: SimulatorApplication, deviceID: String) {
+    guard self.deviceID == deviceID else { return }
+    mergeInstallation(application)
+    recentReplacements.insert(application.bundleID.lowercased())
+  }
+
+  private func mergeInstallation(_ application: SimulatorApplication) {
     let bundleID = application.bundleID.lowercased()
     installedDuringRefresh.removeAll { $0.bundleID.lowercased() == bundleID }
     installedDuringRefresh.append(application)
     removedDuringRefresh.remove(bundleID)
-    recentInstallations.insert(bundleID)
     applications?.removeAll { $0.bundleID.lowercased() == bundleID }
     applications?.append(application)
   }
@@ -74,6 +108,7 @@ final class InstalledAppsStore {
     installedDuringRefresh.removeAll { $0.bundleID.lowercased() == bundleID }
     removedDuringRefresh.insert(bundleID)
     recentInstallations.remove(bundleID)
+    recentReplacements.remove(bundleID)
     applications?.removeAll { $0.bundleID.lowercased() == bundleID }
   }
 
diff --git a/src/LibrarySection.swift b/src/LibrarySection.swift
index 3eb6e9e..bfc345e 100644
--- a/src/LibrarySection.swift
+++ b/src/LibrarySection.swift
@@ -1,12 +1,13 @@
 import SwiftUI
 
 enum LibrarySection: String, CaseIterable {
-  case discover, installed
+  case discover, installed, updates
 
   var title: String {
     switch self {
     case .discover: String(localized: "Discover")
     case .installed: String(localized: "Installed")
+    case .updates: String(localized: "Updates")
     }
   }
 
@@ -14,6 +15,7 @@ enum LibrarySection: String, CaseIterable {
     switch self {
     case .discover: String(localized: "Open-source favorites. Built for your simulator.")
     case .installed: String(localized: "Apps from the catalog on this simulator.")
+    case .updates: String(localized: "Newer versions for your simulator.")
     }
   }
 
@@ -21,6 +23,7 @@ enum LibrarySection: String, CaseIterable {
     switch self {
     case .discover: "safari"
     case .installed: "square.grid.2x2"
+    case .updates: "arrow.triangle.2.circlepath"
     }
   }
 }
diff --git a/src/SidebarView.swift b/src/SidebarView.swift
index 156e658..2c4894a 100644
--- a/src/SidebarView.swift
+++ b/src/SidebarView.swift
@@ -7,6 +7,7 @@ struct SidebarView: View {
   let isChecking: Bool
   let needsXcode: Bool
   @Binding var section: LibrarySection
+  let updateCount: Int?
   let selectedDeviceID: String?
   let startingDeviceIDs: Set<String>
   let selectDevice: (String) -> Void
@@ -32,11 +33,25 @@ struct SidebarView: View {
           Button {
             section = item
           } label: {
-            Label {
-              Text(verbatim: item.title)
-            } icon: {
-              Image(systemName: item.symbolName)
+            HStack(spacing: 8) {
+              Label {
+                Text(verbatim: item.title)
+              } icon: {
+                Image(systemName: item.symbolName)
+              }
+              .frame(maxWidth: .infinity, alignment: .leading)
+              if item == .updates, let count = visibleUpdateCount {
+                Text(count, format: .number)
+                  .font(.system(size: 10, weight: .semibold))
+                  .monospacedDigit()
+                  .foregroundStyle(.white)
+                  .padding(.horizontal, 6)
+                  .frame(height: 18)
+                  .background(Color.accentColor, in: Capsule())
+                  .accessibilityHidden(true)
+              }
             }
+            .frame(minHeight: 18)
             .font(.system(size: 13, weight: section == item ? .semibold : .regular))
             .foregroundStyle(section == item ? Color.accentColor : Color.primary)
             .frame(maxWidth: .infinity, alignment: .leading)
@@ -49,10 +64,13 @@ struct SidebarView: View {
             .contentShape(Rectangle())
           }
           .buttonStyle(.plain)
+          .accessibilityLabel(Text(verbatim: item.title))
+          .accessibilityValue(
+            Text(verbatim: item == .updates ? visibleUpdateCount?.formatted() ?? "" : "")
+          )
           .accessibilityAddTraits(section == item ? .isSelected : [])
           .accessibilityIdentifier("library-\(item.rawValue)")
         }
-        sidebarPlaceholder("Updates", systemImage: "arrow.triangle.2.circlepath")
       }
       .padding(.horizontal, 12)
       .fixedSize(horizontal: false, vertical: true)
@@ -143,12 +161,8 @@ struct SidebarView: View {
 
   private var simulatorListTitle: Text { Text("Simulators") }
 
-  private func sidebarPlaceholder(_ title: LocalizedStringKey, systemImage: String) -> some View {
-    Label(title, systemImage: systemImage)
-      .font(.system(size: 13))
-      .foregroundStyle(.tertiary)
-      .frame(maxWidth: .infinity, alignment: .leading)
-      .padding(.horizontal, 12)
-      .padding(.vertical, 11)
+  private var visibleUpdateCount: Int? {
+    guard let updateCount, updateCount > 0 else { return nil }
+    return updateCount
   }
 }
diff --git a/tests/AppCatalogTests.swift b/tests/AppCatalogTests.swift
index a8cf252..8c87f15 100644
--- a/tests/AppCatalogTests.swift
+++ b/tests/AppCatalogTests.swift
@@ -5,6 +5,7 @@ struct AppCatalogTests {
   static func main() throws {
     try decodeAndSort()
     try localizationAndCompatibility()
+    try compatibleUpdates()
     try rejectInvalidCatalogs()
     print("PASS: catalog decoding, version ordering, language fallback, and compatibility.")
   }
@@ -56,6 +57,40 @@ struct AppCatalogTests {
       !entry.latestVersion.isCompatible(with: "unknown"), "Unknown runtime is not compatible.")
   }
 
+  static func compatibleUpdates() throws {
+    let entry = try decode(apps: [
+      app(versions: [
+        version("1.9.0", minimum: "16.0"), version("1.11.0", minimum: "28.0"),
+        version("1.10.0", minimum: "27.0"),
+      ])
+    ]).apps[0]
+    try require(
+      entry.availableUpdate(from: "1.9.0", runtime: "27.0")?.version == "1.10.0",
+      "Offer the newest compatible build, comparing version components numerically.")
+    try require(
+      entry.availableUpdate(from: "1.8", runtime: "16.4")?.version == "1.9.0",
+      "An older runtime may update to a compatible historical build.")
+    for current in ["1.10", "1.10.0", "1.11.0", "2.0.0"] {
+      try require(
+        entry.availableUpdate(from: current, runtime: "27.0") == nil,
+        "Equal or newer installed versions must never be treated as updates.")
+    }
+    for current: String? in [
+      nil, "", "1.0-beta", "v1.0.0", "1.0.0.1", String(repeating: "9", count: 30),
+    ] {
+      try require(
+        entry.availableUpdate(from: current, runtime: "27.0") == nil,
+        "Unknown and uncomparable installed versions cannot imply an automatic update.")
+    }
+    try require(
+      entry.availableUpdate(from: "1.0.0", runtime: "15.0") == nil
+        && entry.availableUpdate(from: "1.0.0", runtime: "unknown") == nil,
+      "No compatible build must produce no automatic update, rather than falling back to latest.")
+    try require(
+      entry.versions.last?.comparison(with: "1.10.0") == .orderedAscending,
+      "Selecting a historical version must distinguish a downgrade from an update.")
+  }
+
   static func rejectInvalidCatalogs() throws {
     try reject(["schemaVersion": 2, "apps": []], expected: .unsupportedSchema)
     try reject(["schemaVersion": 1, "apps": [app(), app()]])
diff --git a/tests/AppInstallationTests.swift b/tests/AppInstallationTests.swift
index 283a187..79965c8 100644
--- a/tests/AppInstallationTests.swift
+++ b/tests/AppInstallationTests.swift
@@ -16,6 +16,9 @@ struct AppInstallationTests {
       try await stoppedDevice()
       try await uninstallJobs()
       try await uninstallFailure()
+      try versionActions()
+      try await replacementPipeline()
+      try await replacementWhileSwitchingDevices()
       print(
         "PASS: package verification, safe extraction, Simulator binaries, install/open, per-device jobs, cancellation, failures, and cleanup."
       )
@@ -371,6 +374,113 @@ struct AppInstallationTests {
     }
   }
 
+  static func versionActions() throws {
+    let version = InstallationFixtures.version()
+    let cases: [(String?, AppInstallationAction)] = [
+      ("0.9.0", .update), ("1.0", .open), ("2.0.0", .downgrade), (nil, .replace),
+      ("1.0-beta", .replace),
+    ]
+    for (installedVersion, expected) in cases {
+      let installed = SimulatorApplication(
+        bundleID: "org.example.App", version: installedVersion, isUserApplication: true)
+      try InstallationFixtures.require(
+        AppInstallationAction.forVersion(version, installed: installed, allowsChanges: true)
+          == expected,
+        "Choose an action that accurately describes replacing the installed version.")
+      try InstallationFixtures.require(
+        AppInstallationAction.forVersion(version, installed: installed, allowsChanges: false)
+          == .open,
+        "Installed cards keep Open rather than silently replacing an app.")
+    }
+    let system = SimulatorApplication(
+      bundleID: "com.apple.Example", version: "0.9.0", isUserApplication: false)
+    try InstallationFixtures.require(
+      AppInstallationAction.forVersion(version, installed: system, allowsChanges: true) == .open,
+      "Do not offer version replacement for system applications.")
+  }
+
+  static func replacementPipeline() async throws {
+    let directory = try InstallationFixtures.temporaryDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+    let data = try archiveData(in: directory)
+    let app = InstallationFixtures.app(version: InstallationFixtures.version(data: data))
+    let device = InstallationFixtures.device
+    for fails in [false, true] {
+      let commands = InstallationCommands(failsInstallation: fails)
+      let inventory = InstalledAppsStore(load: { _ in
+        [SimulatorApplication(bundleID: app.bundleID, version: "0.9.0", isUserApplication: true)]
+      })
+      await inventory.refresh(for: device)
+      var freshInstall = false
+      let store = AppInstallationStore(
+        installer: AppInstaller(
+          download: { _, destination, _ in try data.write(to: destination) }, command: commands.run,
+          temporaryDirectory: directory.appending(component: "work")),
+        showDevice: { _ in }, didInstall: { _, _ in freshInstall = true },
+        didReplace: { inventory.recordReplacement($0, deviceID: $1) })
+      store.replace(app: app, version: app.latestVersion, on: device)
+      try await InstallationFixtures.eventually {
+        store.phase(appID: app.id, deviceID: device.id) == nil
+      }
+      let simulatorCommands = commands.calls.filter { $0.first == "simctl" }
+      try InstallationFixtures.require(
+        simulatorCommands.count == 1
+          && simulatorCommands[0].prefix(3) == ["simctl", "install", device.id],
+        "Replace through simctl install without an uninstall or erase step.")
+      try InstallationFixtures.require(
+        !freshInstall, "Replacement must not be recorded as a new Discover installation.")
+      try InstallationFixtures.require(
+        inventory.application(bundleID: app.bundleID, deviceID: device.id)?.version
+          == (fails ? "0.9.0" : "1.0.0"),
+        "Only a successful replacement may change the installed version.")
+      try InstallationFixtures.require(
+        (store.error(appID: app.id, deviceID: device.id) != nil) == fails,
+        "Report failed replacements and retain the old installed version for retry.")
+    }
+  }
+
+  static func replacementWhileSwitchingDevices() async throws {
+    let directory = try InstallationFixtures.temporaryDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+    let data = try archiveData(in: directory)
+    let version = InstallationFixtures.version(data: data)
+    let app = InstallationFixtures.app(version: version)
+    let a = InstallationFixtures.device
+    let b = SimulatorDevice(id: "device-B", name: a.name, runtime: a.runtime, state: a.state)
+    let gate = InstallationDownloadGate(data: data)
+    let commands = InstallationCommands()
+    let inventory = InstalledAppsStore(load: { _ in
+      [SimulatorApplication(bundleID: app.bundleID, version: "0.9.0", isUserApplication: true)]
+    })
+    await inventory.refresh(for: a)
+    var completedDevices: [String] = []
+    let store = AppInstallationStore(
+      installer: AppInstaller(
+        download: { try await gate.download($0, $1, $2) }, command: commands.run,
+        temporaryDirectory: directory.appending(component: "work")), showDevice: { _ in },
+      didReplace: { application, deviceID in
+        completedDevices.append(deviceID)
+        inventory.recordReplacement(application, deviceID: deviceID)
+      })
+    store.replace(app: app, version: version, on: a)
+    try await gate.waitForCount(1)
+    await inventory.refresh(for: b)
+    store.replace(app: app, version: version, on: a)
+    store.install(app: app, version: version, on: a)
+    store.uninstall(app: app, on: a)
+    try InstallationFixtures.require(
+      await gate.count == 1, "Replacement shares the existing per-app/device job lock.")
+    await gate.finish(0)
+    try await InstallationFixtures.eventually { store.phase(appID: app.id, deviceID: a.id) == nil }
+    try InstallationFixtures.require(
+      completedDevices == [a.id] && commands.calls.last?.prefix(3) == ["simctl", "install", a.id],
+      "A background update must complete on its captured device.")
+    try InstallationFixtures.require(
+      inventory.deviceID == b.id
+        && inventory.application(bundleID: app.bundleID, deviceID: b.id)?.version == "0.9.0",
+      "A completed update on the previous device cannot replace the selected device's version.")
+  }
+
   static func archiveData(in directory: URL) throws -> Data {
     try Data(
       contentsOf: InstallationFixtures.archive(InstallationFixtures.entries(), in: directory))
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 58ed554..ab37606 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -46,6 +46,7 @@ add_executable(SimStoreInstallationTest AppInstallationTests.swift AppDownloadTe
     "${PROJECT_SOURCE_DIR}/src/AppPackage.swift"
     "${PROJECT_SOURCE_DIR}/src/AppInstaller.swift"
     "${PROJECT_SOURCE_DIR}/src/AppInstallationStore.swift"
+    "${PROJECT_SOURCE_DIR}/src/AppInstallationAction.swift"
     "${PROJECT_SOURCE_DIR}/src/InstalledAppsStore.swift"
     "${PROJECT_SOURCE_DIR}/src/SimulatorApplications.swift"
     "${PROJECT_SOURCE_DIR}/src/SimulatorDiscovery.swift"
diff --git a/tests/InstalledAppsStoreTests.swift b/tests/InstalledAppsStoreTests.swift
index a535db5..14345ed 100644
--- a/tests/InstalledAppsStoreTests.swift
+++ b/tests/InstalledAppsStoreTests.swift
@@ -14,6 +14,7 @@ struct InstalledAppsStoreTests {
       try await retainInstalledAppsForCurrentVisit()
       try await installedVersionsAndMatching()
       try await recordingUninstallationDuringRefresh()
+      try await updateFilteringAndRetention()
       print(
         "PASS: per-device installed apps, filtering, stale responses, errors, and cancellation.")
     } catch {
@@ -323,6 +324,75 @@ struct InstalledAppsStoreTests {
       "The latest completed mutation wins when an app is reinstalled during a refresh.")
   }
 
+  static func updateFilteringAndRetention() async throws {
+    let current = catalog()
+    let store = InstalledAppsStore(load: { device in
+      [
+        application("IO.EXAMPLE.INSTALLED", version: device.id == "A" ? "0.8.0" : "2.0.0"),
+        application("io.example.Available", version: nil),
+        SimulatorApplication(
+          bundleID: "io.example.Unknown", version: "0.8.0", isUserApplication: false),
+      ]
+    })
+    try require(
+      store.updatableApps(in: current, for: device("A")) == nil,
+      "Unknown inventories must not claim no updates.")
+    await store.refresh(for: device("A"))
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.map(\.id) == ["installed"],
+      "Offer updates only for matching user apps with comparable older versions.")
+    try require(
+      store.updatableApps(in: current, for: device("A"), includingRecent: false)?.count == 1,
+      "The sidebar count includes pending compatible updates.")
+    try require(
+      store.updatableApps(in: current, for: device("B")) == nil
+        && store.updatableApps(in: current, for: device("A", state: "Shutdown")) == nil,
+      "Updates belong to a known running device.")
+    store.recordReplacement(application("io.example.INSTALLED", version: "1.0.0"), deviceID: "A")
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.map(\.id) == ["installed"],
+      "Retain a completed update for Open in the current visit.")
+    try require(
+      store.updatableApps(in: current, for: device("A"), includingRecent: false)?.isEmpty == true,
+      "A completed update retained for Open must not inflate the sidebar count.")
+    try require(
+      store.discoverableApps(in: current, for: "A")?.isEmpty == true,
+      "Updating an existing app must not expose it as newly installed in Discover.")
+    store.removeRecentInstallation(bundleID: "io.example.installed", deviceID: "B")
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.count == 1,
+      "Another device's Open must not remove this card.")
+    store.removeRecentInstallation(bundleID: "io.example.installed", deviceID: "A")
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.isEmpty == true,
+      "A successful Open removes a completed update.")
+    store.recordReplacement(application("io.example.Installed", version: "1.0.0"), deviceID: "A")
+    store.clearRecentInstallations()
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.isEmpty == true,
+      "Explicit refresh or navigation ends retained updates.")
+    store.recordReplacement(application("io.example.Installed", version: "2.0.0"), deviceID: "A")
+    try require(
+      store.updatableApps(in: current, for: device("A"))?.isEmpty == true,
+      "A newer installed version must not create a downgrade card.")
+    await store.refresh(for: device("B"))
+    try require(
+      store.updatableApps(in: current, for: device("B"))?.isEmpty == true,
+      "A device with a newer app has no update.")
+
+    let probe = InventoryProbe()
+    let pendingStore = InstalledAppsStore(load: { try await probe.load($0) })
+    let pending = Task { await pendingStore.refresh(for: device("A")) }
+    try await eventually { await probe.calls.count == 1 }
+    pendingStore.recordReplacement(
+      application("io.example.Installed", version: "1.0.0"), deviceID: "A")
+    await probe.finish(0, with: .success(["io.example.Installed"]))
+    await pending.value
+    try require(
+      pendingStore.application(bundleID: "io.example.Installed", deviceID: "A")?.version == "1.0.0",
+      "An older query cannot roll back the version from a completed update.")
+  }
+
   static func eventually(_ condition: () async -> Bool) async throws {
     let deadline = ContinuousClock.now.advanced(by: .seconds(2))
     while !(await condition()) {